Interfacial interactions of the crude oil-reservoir brine-reservoir rock systems with dissolution of carbon dioxide under reservoir conditions

CO2 flooding is considered as one of the most promising enhanced oil recovery (EOR) techniques because it not only effectively enhances oil recovery due to the dissolution of CO2 into the crude oil but also considerably reduces greenhouse gas emissions by sequestrating CO2 in a depleted oil reservoir. Successful CO2 EOR and CO2 sequestration processes are strongly affected by the interfacial interactions among the crude oil, reservoir brine, CO2, and the reservoir rock. However, there are no systematic studies of the interfacial interactions of the crude oil-reservoir brine-reservoir rock systems with dissolution of CO 2 under reservoir conditions. In this dissertation study, an experimental technique is developed to determine the interfacial tension, wettability (i.e., contact angle) and to visualize the interfacial interactions among the crude oil, reservoir brine, reservoir rock and CO2 at high pressures and elevated temperatures. Meanwhile, a wettability measurement technique is successfully developed to determine the contact angle of a fluid-liquid-solid system. In addition, a new dynamic interfacial tension method is applied to study the mass transfer processes of the reservoir brine-CO2 system and the crude oil-CO2 system under reservoir conditions in terms of the measured dynamic and equilibrium interfacial tensions.; For the reservoir brine-CO2 system, crude oil-CO2 system, and crude oil-reservoir brine-CO2 system, the measured dynamic interfacial tension is gradually reduced to an equilibrium value at different pressures and two constant temperatures. For the reservoir brine-CO 2 system or the crude oil-CO2 system, the equilibrium interfacial tension decreases as the pressure increases, whereas it increases as the temperature increases. This is attributed to higher CO2 solubility at a higher pressure but lower CO2 solubility at a higher temperature. For the crude oil-CO2 system, there always exists a constant low interfacial tension as long as the pressure is higher than a threshold value. When CO 2 is introduced into the crude oil-reservoir brine system, the interfacial tension remains almost constant in the pressure and temperature ranges tested in this study. For the crude oil-reservoir brine-reservoir rock-CO2 system, the dynamic contact angle reaches its equilibrium value at different pressures and two temperatures due to the dissolution of CO2. When CO2 is introduced into the crude oil-reservoir brine-reservoir rock system, the equilibrium contact angle is smaller at a lower temperature but larger at a higher temperature. The measured mass transfer Biot number, diffusion coefficient and interface mass transfer coefficient of the reservoir brine-CO2 system are larger at a higher pressure due to a smaller size of the hydrated CO2 molecules. Also, these parameters of the crude oil-CO2 system are larger at a higher pressure because of a lower viscosity of the crude oil.